Kiawah ’ s Pond System
Story by Matt Hill , Lakes Supervisor , Kiawah Island Community Association ( KICA )
Water is no stranger to Kiawah Island — it surrounds us . One would be hard-pressed to visit this sea island and not notice the many ponds that dot its landscape , 124 to be exact . These ponds offer Kiawah Island much more than an attractive aesthetic . They are linked together by a series of pipes creating the Island ’ s storm water drainage system . The ponds ’ primary function by design is to catch and hold storm water runoff before directing the water to the creeks and tributaries around the Island via outfall structures .
There are nine primary outfall structures located at Beachwalker , Bass , Egret , Pintail , Canvasback , Ibis , Willet , Snowy Egret , and Blue Heron Ponds . These outfall structures have flap gates and risers that allow the water levels to be controlled and adjusted . For instance , in a storm situation , the ponds can be drained or lowered to increase their holding capacity for runoff . The gates are normally set in a way that allows water transfer in and out of the ponds at high tide . In general though , the water levels regulate themselves . High tides can flow in , slightly raising the water level . As the tide falls , the pond level falls too until it reaches the set height of the weir wall in the outfall structure . Once the set height is reached , the water stops exiting the pond and is maintained at the normal pool height .
A common misunderstanding regarding Kiawah ’ s pond system is its salinity . The outfalls mentioned above are directly connected to the tidal fluctuations of the Kiawah River . During the majority of the high tides , the tidal amplitude is great enough to bring water into the pond system . This creates a situation where the pond closest to an outfall has a salinity measure similar to the river or creek , sometimes ranging as high as 32 parts per thousand ( ppt ). For reference , ocean salinity is typically 35 ppt .
As you move toward the center of the Island , the ponds become fresher due to rainwater runoff slowing salinity infiltration . These ponds have salinities ranging from 1 ppt to 20 ppt and are considered brackish . No ponds on the Island technically qualify as freshwater , although some freshwater species do reside in a few of the ponds . Freshwater is classified as having a salinity of 0.5 ppt or less . Though salinity may be within this range at certain times of the year ,
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Photo by Kathy Keane